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a. What is the acceleration caused by gravity at the earth's pole?
= The acceleration due to gravity at the pole of the Earth is approximately 9.8 m/s2.
b. What is alternative source of energy?
= Alternative sources of energy include solar power, wind power, hydropower, geothermal energy, biomass, and biofuel.
c. In which two factors does the heat gain or loss by an object depend upon?
= The two factors that affect the heat gain or loss by an object are the temperature difference between the object and its environment, and the rate of heat transfer between the object and its environment.
d. Define converging lens?
= A converging lens is a type of lens that bends parallel rays of light inward, focusing them to a single point. This type of lens is also known as a convex lens because its curved outward shape causes it to gather light.
e. What is transformer?
= A transformer is an electrical device that uses electromagnetic induction to transmit energy between two or more circuits. It is used to convert alternating current (AC) from one voltage to another, and can also be used to isolate circuits, providing electrical isolation. Transformers are widely used in a variety of applications, including power distribution and transmission, as well as signal and data transmission.
f. Write the types of given chemical equation.
= i. C+O2=CO2
= Combination reaction
ii. 2KCLO3=2KCL+3O2
= This is a decomposition reaction.
g. Define neutral salt.
= Neutral salt is a type of salt that does not have any acidic or basic properties. It is composed of equal parts of an acid and a base, so that the pH of the solution is neutral (pH 7). Examples of neutral salts include sodium chloride, potassium chloride, ammonium chloride, and magnesium chloride.
h. Name of two ores of iron.
= 1. Hematite
2. Magnetite
i. Write general formula of alkene.
= Alkene: CnH2n
j. Write the name of two species of silkworm cultivated in Nepal.
= 1. Bombyx mori
2. Antheraea assamensis
k. Write the name of vein in which pure blood flows.
= Superior Vena Cava
l. Write any two chrosomal disorders caused by sex chromosome.
= 1. Turner Syndrome: A chromosomal disorder caused by a missing or incomplete X chromosome.
2. Klinefelter Syndrome: A chromosomal disorder caused by the presence of an extra X chromosome in males.
m. What is the part of plant called that is used for root in grafting?
= The part of the plant used for root in grafting is called the rootstock.
n. Mention any two effects of water pollution.
= 1. Ecosystem Disruption: Pollutants in water can disrupt the balance of aquatic ecosystems, killing off fish and other aquatic species and creating imbalances in the food chain.
2. Human Health Risk: Contaminated water can spread illnesses and diseases, such as cholera, dysentery, typhoid and hepatitis, when it is ingested or comes in contact with the skin.
o. In which eras do owl and flowering plants evolved?
= Owls evolved during the Eocene Epoch, which lasted from 55-33.9 million years ago, while flowering plants evolved during the Cretaceous Period, which lasted from 145-66 million years ago.
(Group 'B')
2. Kathmandu lies at high altitude than biratnagar from sea level. Where between two places does an object have most weight? Give reason.
= The object would have the same weight at both places, because weight is determined by gravity and gravity is a constant force. That is, the same gravitational force is exerted on an object at Kathmandu and Biratnagar, no matter the altitude.
3. In the context of Nepal, hydropower should be given more priority rather than fossil fuel. Why? Justify with two reason.
= i. Hydropower is a renewable energy source, meaning it has the potential to be a sustainable and clean source of energy that can be used again and again. In contrast, fossil fuels are non-renewable resources, meaning they will eventually run out.
ii. Hydropower is a cost effective energy source as it does not require any fuel inputs or expensive infrastructure. This makes it a much more affordable option for countries such as Nepal, which have limited resources.
4. What happens if an egg is kept in two beakers containing pure water and saturated salt solution? Why?
= If an egg is kept in two beakers containing pure water and saturated salt solution, the egg will eventually float in the beaker containing the saturated salt solution. This is because the egg is denser than the pure water, but less dense than the saturated salt solution, so it will float in the salt solution.
5. Mention any two reasons why nicrome wire is used in electric heaters.
= i. Nickel-chrome wire (also known as Nichrome wire) is commonly used in electric heaters because of its excellent electrical resistance and high temperature resistance.
ii. It does not corrode or oxidize easily and is a good conductor of electricity, making it an efficient and effective heating element.
6. Write the balanced chemical reaction between Almunium metal and dilute hydrochloric acid. Mention the type of reaction with reason.
= Aluminium + Hydrochloric Acid -> Aluminium Chloride + Hydrogen
Reaction Type : Single Replacement (Displacement) Reaction
Reason : Aluminium (a more reactive metal) displaces Hydrogen (a less reactive element) from Hydrochloric Acid in order to form Aluminium Chloride and Hydrogen.
7. Write a structural formula of glycerol and write any one use of ethly alcohol.
= Structural formula of Glycerol:
CH2OH-CHOH-CH2OH
One use of Ethyl Alcohol:
Ethyl Alcohol is used as a solvent in the production of cosmetics, pharmaceuticals, and perfumes.
8. Write any two function of organic fertilizer.
= i. Enhances Soil Health: Organic fertilizers add essential nutrients like nitrogen, phosphorus, and potassium to the soil. These nutrients help encourage the growth of beneficial soil microorganisms like bacteria and fungi, which improve soil texture and fertility.
ii. Improves Plant Health: A healthy soil environment encourages healthy plant growth. Organic fertilizers contain natural plant hormones that stimulate root and leaf growth. They also provide a slow and steady release of nutrients, which helps plants absorb the nutrients they need over a longer period of time.
9. Write two differences between axon and dendrites.
= i. Axons are generally much longer than dendrites and can be up to several feet in length, while dendrites tend to be much shorter.
ii. Axons transmit electrical signals away from the neuron cell body, while dendrites receive electrical signals from other neurons and transmit them to the neuron cell body.
10. Write two difference between systemic and pulmonary blood circulation.
= i. Systemic circulation involves the circulation of blood from the left ventricle of the heart to the body tissues and organs and back to the right atrium of the heart. Pulmonary circulation involves the circulation of blood from the right ventricle of the heart to the lungs and back to the left atrium of the heart.
ii. Systemic circulation carries oxygenated blood, while pulmonary circulation carries deoxygenated blood.
11. Write any two characterstics of modern periodic table.
= i. Group and Periods: The modern periodic table is arranged in order of increasing atomic number, with elements placed in groups (columns) and periods (rows) that share similar properties.
ii. Element Families: The modern periodic table classifies elements into families that share similar properties, such as alkali metals, transition metals, and noble gases.
12. Write any two differences between a drone bee and a worker bee.
= i. Drone bees are male bees, while worker bees are female bees.
ii. Drone bees do not have a stinger, while worker bees do.
13. Why is meteor generally finished before reaching the earth surface?
=Meteoroids typically enter Earth's atmosphere at high speeds, and because of the friction created with the atmosphere, they heat up and become vapourised before they can reach the Earth's surface.
(Group 'C')
14. What is the condition for an object to sink in water? Pistons A1 and A2 have cross-sectional areas of 50cm2 and 0.2m2, respectively. How much load can lift in piston A2 if 250 N force applied on piston A1?
= For an object to sink in water, it must have a density greater than the density of the water.
The load that can be lifted in piston A2 is 12500 N, since A2 has a cross-sectional area of 0.2 m2 and A1 has a cross-sectional area of 50 cm2, the force applied to A1 is 250 N. Therefore, the force on A2 is 250 N x (0.2m2/50cm2) = 12500 N.
15. Prove that heat loss or gain by an object is equal to the product of mass of object, specific heat capacity and change in temperature.
= Let m = mass of the object (in kg)
C = specific heat capacity of the object (in J/kg-K)
ΔT = change in temperature of the object (in K)
Heat gained (Q) or lost (Q) by the object is:
Q = m x C x ΔT
Proof:
The amount of heat gained or lost (Q) by an object is related to the heat capacity and the change in temperature. Heat capacity (C) is defined as the amount of heat (Q) required to raise the temperature of an object by 1K.
Hence, the amount of heat (Q) required to raise the temperature of an object by ΔT is given by:
Q = C x ΔT
Now, since the mass (m) of the object is also involved, the heat gained (Q) or lost (Q) by the object is:
Q = m x C x ΔT
Hence, it is proved that heat loss or gain by an object is equal to the product of mass of object, specific heat capacity and change in temperature.
16. Why is glass called fourth state of matter? Write any two applications of water glass and lead crystal glass.
= Glass is called the fourth state of matter because it has properties of both solids and liquids. It is a solid material that is formed from a liquid at high temperatures.
Two uses of water glass are as a sealant and as a preservative for food. Lead crystal glass is used for making decorative items such as vases and glasses, as well as for high-end optics for research purposes.
17. What will you recommend to your neighbors to help reduce soil pollution? Write any six suggestion.
= 1. Avoid using chemical-based fertilizers and pesticides.
2. Implement organic farming methods, such as crop rotation and composting.
3. Minimize the use of vehicles to reduce air pollution, which can lead to soil contamination.
4. Plant trees and shrubs to help absorb pollutants from the soil.
5. Properly dispose of all hazardous materials, such as motor oil, paint, and batteries.
6. Use natural alternatives to chemical-based products, such as vinegar or baking soda.
(Group 'D')
18. Draw a ray diagram of an image formed when an object is placed at a distance of 10cm from a convex lens having focal length 20cm. Write any two nature of image. Calculate the power of lens.
= Ray diagram:
The image formed will be a real, inverted and enlarged image.
Power of lens = 1/F = 1/20cm = 0.05D
19. Write the name of main chemical which destroy ozone layer. How ozone layer is depleted by that chemical? Describe with chemical equation.
= The main chemical responsible for the destruction of the ozone layer is chlorofluorocarbon (CFC). When CFC molecules, such as CFCl3, CF2Cl2, CFCl2Cl, and CF3Cl, reach the stratosphere, they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms that then react with ozone molecules. The following chemical equation represents the reaction:
O3 + Cl → O2 + CLO
CLO then reacts with an oxygen molecule to form a chlorine atom and two molecules of oxygen, as represented in the following chemical equation:
CLO + O → Cl + O2
The chlorine atom then reacts with another ozone molecule and the cycle repeats, resulting in the destruction of ozone molecules. This process is known as the chlorine catalytic cycle and is responsible for the depletion of the ozone layer.
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